Well, Tenshinhan at the fake androids arc reacted to Gero's eye laser in a similar manner to base Goku, who although being affected by the disease, was still likely stronger than his past 3 years self, so I would envision Tenshinhan as in the same ballpark of base sick Goku as that could imply they have similar reflexes and speed reaction, which are generally a sign of approximated fighting powers, and that according to my numbers would give Ten a 4,000,000 figure or so. Kuririn is given as the strongest earthling at the Boo arc by Yamcha and while he hasn't seen Tenshinhan for 7 years this should at least put him at the top in the Cell arc, but there's still a limit as Kuririn should be still weaker than the Android's arc base Saiyajins, logically speaking. So at 4,500,000 or so would be a fine placement, enough to contend against final form Freeza if he's restricted to a pretty low percentage of his power, but more than it and it's already too much for him.
And I believe that's his peak. He trained for the Budôkai when he knew Goku would be taking part, but the fact that he grew a hair means he isn't that seriously with fighting anymore, so at most I think that he has maintained such power. Maybe I can see him scratching the 5,000,000 and slightly above but that's it.
